1. Field of the Invention
The present invention relates to a polyurethane resin moulding for a vehicle interior part and a method of manufacturing the same. Specifically, the present invention relates to a polyurethane resin moulding capable of suppressing a rise of a temperature on a surface of a vehicle interior part and a maximum surface temperature compared with a conventional art when the vehicle interior part is exposed to direct sunlight, and capable of lessening hotness when a passenger touches the surface of the vehicle interior part, and relates to the method of manufacturing the polyurethane resin moulding for the vehicle interior part.
2. Description of the Related Art
Generally, when parking a vehicle outside and receiving direct sunlight for a prolonged time especially in summer, a room temperature in the vehicle reaches nearly 80° C. A surface temperature of a polyurethane resin moulding for a vehicle interior part and the like increases as the room temperature increases. For instance, a surface temperature of a steering wheel reaches nearly 80° C. Although an air conditioner, for instance, is actuated to lower the room temperature so as to get into the vehicle, the surface temperature of the steering wheel is not lowered immediately while the room temperature is lowered relatively easily. Therefore, a substantial amount of time is required until the surface temperature of the steering wheel is lowered so as to hold and operate the steering wheel.
Thus, conventionally, it has been required to lessen hotness when a passenger touches the surface of the steering wheel, i.e. suppress the temperature rise on the surface of the steering wheel and decrease the maximum surface temperature. The following method has been suggested as the method of suppressing the rise of the temperature on the surface of the polyurethane resin moulding.
Japanese Patent Unexamined Publication No. H11-263872 describes a method combined with a thermal barrier coating and an infrared absorption pigment for a mold coating. In this method, it is possible to suppress a rise of an atmosphere temperature around a product by avoiding an influence of infrared light reflected by air convection in open space. While, a surface temperature of a product in closed space in a vehicle decreases only by 1 to 2° C. since the atmosphere temperature in the vehicle increases as time passes because of almost no air convection. Accordingly, there is little difference with regard to hotness when touching the surface of the product compared to a product not employing the thermal barrier coating and the infrared absorption pigment.
Japanese Patent Unexamined Publication No. 2002-000399 describes an example using a heat storage material. A melting point of the heat storage material is determined to be between 10 to 35° C. lower than human body temperature. Thus, in view of a relationship between room temperature and human body temperature, a mechanism to maintain a certain temperature around the melting point of the heat storage material is adopted so as to feel cool in summer and feel warm in winter. However, an effect of the heat storage material is hardly expected in closed space in a vehicle where the room temperature reaches nearly 80° C.
Japanese Patent Unexamined Publication No. 2007-168550 describes an example using shirasu balloons in order for heat insulation. However, the shirasu balloons are used for a heat insulation coating used for outer walls of a freezer of a refrigerator car, of which an intended purpose is considerably different from the present invention.